We are often asked about anodizing. First, what is anodizing? Anodizing is an electrochemical process that converts the metal surface into a decorative, durable, corrosion-resistant, anodic oxide finish. Anodizing is accomplished by immersing the aluminum in an acid electrolyte bath and passing an electric current through the material. A cathode is mounted to the inside of the anodizing tank; the aluminum acts as an anode so that oxygen ions are released from the electrolyte and combine with the aluminum atoms at the surface of the part. Anodizing is, therefore, a matter of highly controlled oxidation.
Anodize thicknesses are most often defined or specified using the aluminum association designation system where:
The classifications above are for clear anodize, which is the anodize finish most often utilized for welded aluminum systems. In addition to clear anodize (which is devoid of color) there are color anodize finishes and these can be obtained in a multitude of colors. For the products we offer, the only color anodize finish we recommend/provide is dark bronze. The designation most often used for it is A44, denoting a Class 1 Dark Bronze Anodize finish with a minimum thickness of 0.7 mil. The fabrication process for welded products like ours requires that the anodized layer be removed in order to weld components together. While the weld on clear anodize products is acceptable unfinished, the weld on a product with a color anodize finish must be touched up with a paint to hide the welded seam. We have concluded that dark bronze is the only color anodize for which an acceptable touch-up paint can be provided.
The anodizing process steps include racking, cleaning, etching, desmutting, anodizing, sealing, unracking, packing and lab testing. The following video, courtesy of Frontier Aluminum, provides a glimpse into the anodizing factory.